Definitely the Atlanta, she fires so fast and everyone knows it. If I see it then I fire at it given I can hit it at a good angle.
Cruisers in general. Especially the US cruisers where they have a nice fleshy citedal.
Premiums. My only premium is the Arizona, may get more I haven’t decided yet. I’ve noticed in the Arizona and me being matched against premiums that people (including me) tend to fire at premiums just because they are something different from stock ships. I’ll be in the Arizona and be sniped cross map from some tier 8 ship when there are ships much closer to that ship that I know have been spotted. And I’m not even broadside

Lyon is wayyy to OP. We had a arizona, Colorado, Leander and some destroyer go up against a Lyon. After that battle I (the Arizona) was sunk the Colorado had about 1000 HP remaining after a single hit citadeled it probably 2-3 times. The Leander was sunk and the destroyer unsuccessfully torpedoed it only hitting once or twice. The destroyer itself being halfed in HP. After they finally sunk the Lyon (with its final shots crippling the Colorado) an enemy Colorado came around the corner and that didn’t help matters